Tinted polymeric films, and particularly tinted polymeric films made of a polyester, find utility in a broad range of applications. These films, for example, can be applied to a base transparent substrate (e.g., a window or auto glass pane) to provide a neutral color tint to the window or auto glass. They can also used to tint the surface of a display device, mirror, or other piece of optical equipment.
One method for tinting a polymeric base film employs dyeing the base film with one or more color dyes. Typically in such methods, the neutral color, or “tint,” is obtained by imbibing (or blending) the base film material with a combination of yellow, red and blue dyes. While these dyed films generally retain a high clarity and a low haze, prolonged exposure to ultraviolet radiation (which occurs naturally during outdoor use or by exposure to fluorescent light or other UV-emitting light source) can cause significant degradation of the dye molecules and lead to tinting color alteration, tinting power deterioration, bleachings, and reduced light transmission.
Another method sometimes employed for tinting a polymeric film is to apply a pigmented coating to the surface of a base polymeric film. Generally, such coatings are applied as thin layers and employ a relatively high pigment concentration to achieve a desired tint level. These highly-concentrated pigment coatings can suffer myriad processing and performance drawbacks. For example, the high pigment concentrations necessary to achieve requisite tinting strengths are difficult to uniformly disperse within the thin coating, and these high surface pigment concentrations generally suffer faster environmental deterioration. Moreover, such pigmented coatings typically suffer greater haze and reduced clarity.
There exists, therefore, a need for a pigmented film that is environmentally stable (i.e., color-stable or colorfast), that is easily manufactured and that exhibits low haze and high clarity.